1. Field of the Invention
The present invention relates to an image forming apparatus using a thermal print head. More particularly, the present invention relates to a method and device for adjusting an image alignment of an image forming apparatus that uses one thermal print head for applying heat to first and second sides of a medium in order to print an image.
2. Description of the Related Art
Thermal printers use a thermal print head to apply heat to an ink ribbon contacting a medium to transfer the ink of the ribbon to the medium, or apply heat to a medium coated with ink capable of presenting color when heat is applied.
FIG. 1 is a view of a heat-sensitive medium according to the related art.
Referring to FIG. 1, a heat-sensitive medium includes a base sheet 11, a first side 10a, a second side 10b, and a reflective layer 13. Ink layers of different colors are formed on first and second sides 10a and 10b. For example, yellow and magenta layers may be sequentially formed on the first side 10a, and a cyan layer may be formed on the second side 10b. The base sheet 11 may comprise a transparent material. The reflective layer 13 reflects light, such that a color image can be seen from the first side 10a. 
FIG. 2 is a schematic view showing a construction of an image forming apparatus using a thermal print head according to the related art.
Referring to FIG. 2, an image forming apparatus includes a medium 200, a driving roller 210, a driven roller 220, a platen roller 230, and a thermal print head 240.
A motor (not shown) rotates the driving roller 210 to convey the medium 200, which is interposed between the driving roller 210 and the driven roller 220.
The thermal print head 240 applies heat to the conveying medium 200, for printing yellow, magenta and cyan data. The platen roller 230 is faced with the thermal print head 240 with the medium 200 interposed there between. The platen roller 230, as it rotates when the medium is conveyed, supports the medium 200 that receives heat from the thermal print head 240 to provide color printing.
In order to print the yellow, magenta, and cyan data with one thermal print head 240, the thermal print head 240 must apply the heat to the first and second sides 10a and 10b of the medium 200.
As described above, when one thermal print head is used to apply heat to the first and second sides of the medium, a mechanical deviation or a medium conveying path difference is generated, such that the printed areas on the first side and second side of the medium are not aligned with each other and thereby the required colors are not accurately placed in the printed image.
Therefore, a need exists for aligning both sides of a printed medium such that the colors are accurately placed in the printed image when one thermal print head is used.